, 1978; Cernakova et al., 1991; Piutti et al., 2003). Roxadustat nmr Heterogeneous distribution of herbicides in field crops may lead to local maxima of herbicide concentration that exceed reported mean values (Marsh et al., 1978) but current and previous data suggest that the impact of MCPA and Bentazon on oxygen-dependent cellulose and cellobiose degradation is minimal under environmental concentrations. 16S rRNA gene transcript numbers of total soil Bacteria and five family-level taxa of Bacteria that have previously been identified as active members of the cellulolytic and saccharolytic community of the same soil (Schellenberger et al., 2010) were determined in soil samples of cellulose-supplemented

microcosms using reverse transcriptase quantitative PCR (RTqPCR). In the oxic, cellulose-supplemented microcosms, fungal hyphae grow on the cellulose sheets, whereas in anoxic treatments,

fungal hyphae were not observed (data not shown). Thus, it is very likely that fungi contributed to aerobic cellulose degradation. The metabolic response to Bentazon and MCPA of well known and novel, i.e. as yet uncultivated, taxa that have all been proven to contribute to cellulose and cellobiose degradation in the investigated soil (Schellenberger et al., 2010) was evaluated to reveal the taxa that may cause the reduced degradation rates under anoxic conditions. The specificity of the utilized RT qPCR assays has been demonstrated previously in the same soil (Schellenberger et al., 2011). In the presence of 2.4 μmol gsoil find more DW−1, Bentazon and MCPA, transcript numbers of total soil Bacteria and all analysed family-level taxa were lower in both oxic and anoxic microcosms at the end of the experiment

compared with herbicide-free microcosms (Fig. 3; Table 2). Reports about a reduction VAV2 of microbial growth in pure culture by both herbicides support these findings (Cernakova et al., 1991; Ahtiainen et al., 2003; Cabral et al., 2003; Galhano et al., 2009). Transcript numbers of Planctomycetaceae and uncultured ‘Sphingo’ (Bacteroidetes) were significantly lower under oxic conditions, whereas those of uncultured ‘Cellu’ (Bacteroidetes) and Clostridia of group I (Clostridiaceae; according to Collins et al., 1994) were significantly lower under anoxic conditions (Table 2). Most known anaerobic cellulolytic bacteria that have been isolated belong to Clostridia group III (Collins et al., 1994). Clostridiaceae assimilated carbon from supplemented 13C-enriched cellulose and were metabolically stimulated under anoxic conditions in the same soil (Schellenberger et al., 2010, 2011). Development of primers that exclusively target these organisms failed. Thus, it cannot be excluded that the metabolism of not only Clostridia of group I but also group III was inhibited by herbicides.